The invention relates to a housing part for a ventilating fan with an axial rotation shaft, wherein a number of housing parts can be placed radially round the ventilating fan so as to form a substantially cylindrical housing.
The above stated housing parts are applied in for instance cooling devices, for instance for incinerator plants. Such a cooling device consists of a frame on which a large number of heat exchangers are placed. Placed under these heat exchangers is a fan which has a diameter of for instance 10 m. Housing parts are placed round this ventilating fan in order to enable large amounts of air to be drawn in and blown through the heat exchangers located thereabove.
It is known that the housing for the ventilating fan is constructed from four or eight housing parts. These housing parts can be manufactured from wood, concrete, steel or polyester. Since a limited number of housing parts is used to assemble a housing, the housing parts are specifically manufactured for a specific fan diameter. The wall parts all take a single-walled form,
The above stated known housing parts have a number of drawbacks. First of all, the wall parts are easily set into vibration, which can result in mechanical damage because they are single-walled. This also causes additional noise which, in view of current standards, is undesirable. The wall thickness would have to be increased to prevent this, but with the usual materials this can result in very large masses of the wall parts, whereby the construction to which these wall parts have to be fixed must take an extra-strong form.
Between four and eight housing parts have normally been used heretofore to assemble the housing. As a consequence of the large fan diameters, the dimensions of the housing parts are correspondingly large. This therefore has its drawbacks for transport and handling during fitting.
It is an object of the invention to obviate the above stated drawbacks.
This is achieved according to the invention with a housing part which comprises:
an inner wall;
an outer wall placed at a distance from the inner wall; and
connecting walls extending between the inner wall and the outer wall;
wherein the inner wall, the outer wall and the connecting walls define a closed space.
The housing part thus takes a double-walled form. The housing part hereby has a relatively great strength compared to a single-walled housing part, while the weight is relatively low. Because the housing part takes a double-walled form the housing part will cause fewer vibrations and therefore less noise. In addition, the weight is relatively low, thus simplifying assembly.
A preferred embodiment according to the invention comprises at least one strengthening bush which is arranged with the one end on the inner wall and with the other end on the outer wall. The inner wall and the outer wall are mutually connected by the strengthening bushes, whereby the housing part is given additional strength.
The at least one strengthening bush is preferably arranged such that in the formed housing the strengthening bush lies substantially in the same plane as the outer ends of the ventilating fan.
Air turbulences will occur around the extremities of the ventilating fan whereby a housing part could begin to vibrate and thus also cause noise. By now arranging the strengthening bushes such that they lie at the same height as the outer ends of the ventilating fan the housing part will be strengthened locally, whereby vibrations resulting from the air turbulences are prevented.
In another pref erred embodiment according to the invention coupling means are arranged on either side for coupling to an adjoining housing part.
A housing for a ventilating fan is constructed by placing the housing parts against each other around the fan. It is advantageous herein to be able to couple the adjoining housing parts relative to each other, so that they cannot shift relative to each other.
The coupling means preferably comprise a groove arranged on a first side of the housing part and a rib which is arranged on a second side of the housing part and which can be coupled with the groove of an adjoining housing part. By now sliding the rib of one housing part into the groove of an adjoining housing part these housing parts are coupled relative to each other.
In yet another embodiment according to the invention metal parts are arranged in at least one of the walls. These parts can for instance be used to secure bolts or screws therein with which the whole housing part can be fixed or, for instance, two housing parts can be fixed to each other.
In a preferred embodiment according to the invention the closed space is filled with a foamed material. An additional strengthening of the housing part is hereby obtained and the foam, owing to its structure, contributes toward extra noise reduction.
A housing part according to the invention is preferably manufactured by rotation moulding. Preferred materials here are polyethylene or polypropylene.
In yet another embodiment according to the invention the inner wall and the outer wall comprise a first curvature around a first axis of curvature. The inner surface of an assembled housing will hereby better approximate a cylinder surface, thereby reducing vibrations.
In a further preferred embodiment according to the invention the inner wall and the outer wall comprise a second curvature around a second axis of curvature, wherein the second axis of curvature lies perpendicularly of the first axis of curvature. The housing formed with such housing parts therefore has an outward protruding edge, whereby the supply of air is better guided.
The width of a housing part is preferably less than 2 m. The housing parts can hereby be readily placed in a transport container, whereby the housing parts can be transported easily over large distances.
The invention further comprises a housing for a ventilating fan with an axial rotation shaft, which housing comprises:
a first number of housing parts according to the invention placed against each other radially around the ventilating fan; and
fixing means for holding the housing parts fixed against each other.
The fixing means can be for instance bolts and nuts extending through edges of two adjoining housing parts. Preferably however, the fixing means comprise a tensioning belt extending around the housing. A cylinder shape results automatically from placing of the housing parts against each other and then clamping them with a tensioning belt.
In another embodiment according to the invention the housing comprises a second number of housing parts placed against each other and in the line of the first number of housing parts according to the invention.
When air is drawn by the ventilating fan through a housing and then blown for instance through heat exchangers, the air must be blown back again into the environment. By now placing a second number of housing parts in the line of the first number the air is guided into the environment, whereby further noise reduction is obtained.